A typical semiconductor device has a semiconductor base or substrate, i.e. a semiconductor chip, and an insulating substrate on which the semiconductor chip is mounted. The semiconductor chip is connected or bonded with the insulating substrate via solder. In such a semiconductor device having a solder bonding portion, when a calorific or heating value of the semiconductor chip becomes a heating value that is beyond a melting point of the solder, the solder melts and a function of the semiconductor device stops. For this reason, an operating or working temperature of the semiconductor device must be at least under the melting point of the solder. Here, as the solder, for example, a typical lead-free solder of Sn—Ag—Cu is used, and its melting point is about 220° C.
The higher the power of a circuit including the semiconductor device, or the higher the reliability required of the semiconductor device (such as stability with time, thermal stability (heat resistance), and moisture resistance), the higher the insulation performance is required. As the thermal stability, thermal stability in a case where current used in the semiconductor device is large and heat produced in the semiconductor base becomes great, is included. Such a semiconductor device that produces the large heating value and needs high reliability has been required recently.
To meet these requirements, there has been proposed a technique in which the semiconductor chip is directly connected or bonded with the insulating substrate without using the solder in Japanese Patent Provisional Publication No. 2004-014599 (hereinafter is referred to as “JP2004-014599”). In a semiconductor device in JP2004-014599, a surface of an electrode of the semiconductor chip and a surface of a circuit pattern on the insulating substrate are formed by the same material. Then by applying ultrasonic vibration with pressurization under a condition in which the electrode surface and the circuit pattern surface face each other, the both surfaces are directly bonded with each other with solderless connection.